1. Field
The present disclosure relates to an electronic element package and a method for manufacturing the same.
2. Description of Related Art
Recently, with the recent rapid development of mobile communications devices, the demand for macrofilters, oscillators, and other components has increased. For example, bulk acoustic wave (BAW) resonators have been regularly used to implement macrofilters, oscillators, and other components. Using BAW resonators have advantages such as enabling mass production at low cost and allowing for macrominiaturization. Furthermore, BAW resonators enables a high quality factor to be obtained and may be used in macrofrequency bands.
In general, because performance of resonators (vibrators) of BAW resonators degrade at a bonding temperature of 500° C. or more, the BAW resonators need to be hermetically sealed at a low temperature of 500° C. or less. Thus, thermal diffusion bonding, eutectic bonding or silicon direct bonding may be applied.
Furthermore, BAW resonators often use thermal diffusion bonding in a cap bonding process. Thermal diffusion bonding is defined as a method of spreading materials to be bonded, for example, bonding metals, on two surfaces of wafers and pressing the wafers using heat and strong force to bond the wafers. The strong force first functions to press the wafers together to have a gap having a nano size or less so that the spread bonding metals are in close proximity to each other and fuse together. When the pressed wafers are heated, the bonding metals formed on the respective wafers fuse together so that the wafers may be bonded.
In this example, the spread bonding metals represent membrane thickness distribution within the wafers depending on membrane conditions, and the thicknesses of the wafers that form a base of the bonding metals and have a constant degree of thickness distribution. In order to press the wafers having such thickness distribution against each other, a high degree of force is required, and a bonding metal that has high ductility and that may be relatively easily transformed by the same degree of force is needed. Furthermore, equipment able to perform a bonding process requires a high degree of pressure. Moreover, inch-up processes for substrates are required such that microelectromechanical systems (MEMS) devices including up-to-date BAW resonators are of reasonable cost. For the inch-up processes, bonding pressure needs to be increased in proportion to inch-up.
Furthermore, such thermal press bonding may be performed under the condition that a surface to be bonded is required to have a surface in a pure state in which oxidation has not occurred. Thus, Au—Au diffusion bonding is used, in which oxidation barely occurs and provides excellent ductility at high temperatures and under atmospheric conditions. Use of Au—Au diffusion bonding results in an increase in manufacturing costs.